Sustainable Mortar Incorporating Municipal Solid Waste Incineration Fly Ash and Bottom Ash

The Pulau Pangkor plant is one of five small-scale incinerators in different locations in Malaysia. Due to the influence of waste components on the physical and chemical properties of resulting municipal solid waste incineration ash, fly ash (MSWI-FA) and bottom ash (MSWI-BA), the ash of each plant needs to be studied separately. Therefore, this study aims to investigate the effect of using Pulau Pangkor MSWI-FA as a supplementary cementitious material and MSWI-BA as a partial replacement for fine aggregate on mortar performance. Several experiments were conducted to evaluate the material properties, as well as the properties of fresh and hardened mortars, using 5-20% MSWI-FA and 5-25% MSWI-BA replacement ratios. The inclusion of MSWI-FA increased mortar flow by up to 16%, whereas the addition of 25% MSWI-BA reduced flow by up to 76% relative to the control mix. Replacing cement with MSWI-FA reduced compressive strength by 6%–26% across the range of replacement levels, due to MSWI-FA's lack of pozzolanic properties. The results also indicated that lower ash density significantly reduced the resulting mortar density by up to 23%. The higher water absorption of MSWIA also increased the mortar's absorbency; the effect of MSWI-BA was higher. In conclusion, this work provides important insights into the future applications of MSWIA in contexts requiring lightweight, highly absorbent additives with low compressive strength.